1. Field of the Invention
This invention pertains to automatic controls for operating an engine in an unattended situation and specifically for starting and then stopping an engine at periodic intervals.
2. Description of the Prior Art
A producing oil well is normally produced utilizing a continuously running natural gas or butane powered engine. Such an engine is conventionally connected to a pumping unit that could pump a well dry if operated at full efficiency. This is because the oil which is pumped from the well normally does not flow into the well from the adjacent formation at nearly the rate to match the production capacity of an efficiently operated pumping unit. The permeability of the formation, the formation pressure, the oil viscosity and the other environmental factors involved acting together to naturally fill a well typically operate to fill the well at about one-third of the rate at which the well can be efficiently produced.
In order to prevent the pumping equipment from pumping the well dry, the pumping equipment must somehow be restrained. This is done typically by restricting the pump or by choking it against full stroke operation or by operating the engine at a lesser than full rpm.
It is recognized that continuous operation of the engine and the related pumping equipment is not only inefficient if not required for production purposes, but also wears out the equipment faster than if the equipment were operated periodically or at intervals. The reason that equipment is not operated at intervals is due primarily to two factors: many sites are remote from personnel and are difficult to manually operate on a periodic basis and there is little incentive to efficiently operate such equipment because of the ready availability of fuel at the source.
However, it is now believed that operating the well at intervals actually is a more efficient production method than a continuously pumped well. In addition, the wear and tear on the equipment as well as the periodic maintenance makes it well worthwhile to operate the equipment periodically rather than continuously and even permits the use of equipment for longer periods of time before maintenance is required provided that a reliable and inexpensive control system is available for starting and stopping the engine at periodic intervals.
The automatic control apparatus for starting and stopping an unattended motor can be too complicated. The more mechanical parts, involved, the more likely that there will be a malfunction. For example, U.S. Pat. No. 2,924,209 reveals an apparatus allegedly capable of starting and stopping an engine without manual attention in an application such as running an engine at an oil well pump location; however, the structure is bulky and complex. It is not known to have been commercialized, perhaps for that reason. U.S. Pat. Nos. 2,634,682 and 2,991,860 reveal other complex control apparatus for a similar purpose.
U.S. Pat. No. 2,991,370 reveals a representative state-of-the-art system designed to start the engine of an automobile at a preselected time to permit the engine to warm up prior to use. U.S. Pat. Nos. 3,248,555; 3,538,898; and 3,942,024 reveal other control apparatus for a similar purpose.
The following patents disclose the use of a vacuum switch to deenergize a starter motor once an engine has started: U.S. Pat. Nos. 2,497,462; 2,948,104; and 2,949,105. A system using a thermal device for such purpose is shown in U.S. Pat. No. 2,174,101.
Finally, a sophisticated, but extremely complex, automatic control system for a gasoline-powered internal combustion engine is shown in U.S. Pat. No. 4,013,056.
Therefore, it is a feature of the present invention to provide a relatively trouble-free and economical automatic start/stop control device for unattended operation of an engine using simplified connections with readily available components.